Tea is one of the most popular beverages worldwide. Whereas epidemiological studies have so far yielded inconclusive results, laboratory studies by us and others clearly indicate that green and black tea extracts inhibited carcinogenesis in animal models. In this project, we plan to further investigate the inhibitory actions of green an black teas and their components on nitrosamine-induced carcinogenesis in animal models with the following specific aims: 1. To determine the effects of green and black tea extracts and selected tea components on lung, forestomach, and esophageal carcinogenesis induced by specific nitrosoamines in animal models. The dose-response of the active components given at different stages of carcinogenesis will be studied systematically. 2. To elucidate the mechanisms of the inhibition of carcinogenesis by tea and tea components in the above models. Parameters related to their antioxidative, nucleophilic, and other properties pertaining to the carcinogenic processes will be examined. 3. To understand the biological effect of (-)-epigallocatechin gallate and other tea components by studying their absorption, metabolism, bioavailability, and tissue levels. 4. To fractionate green and black tea components, characterize their properties, determine their activities in short-term assays and prepare selected compounds in large quantities for the above studies. The project is expected to provide information fundamental to the understanding of the relationship between tea consumption and carcinogenesis. It will develop theoretical basis and laboratory methods for future epidemiological and intervention studies on tea and human cancer.